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Paul Spencer

DIY audio: what are you building?

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55 minutes ago, Batty said:

Yes, purchased the bare boards and downloaded a partial BOM for Mouser parts and found the remaining parts.

Case is coming from Italy.

All courtesy of DIY Audio.

 

It is the Yarra Pre amp.

 

Good work. I have, on a number of occasions , built components with assembled boards. 

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Posted (edited)

After some positive results from using rubber blocks from Bunnings l decided to take it to the next level and go maglev. So got busy on the lathe, studied up and invested in some ring magnets and come up with these.3AD325FF-8BAC-4885-A46F-1A2C0129FEC7.thumb.jpeg.575d9c2f75c4507b60192430562156ab.jpegB35AC26F-E482-4232-A004-765A74C792C8.thumb.jpeg.aa2fa499fa6dcbb037fdca93ad7d45ae.jpegF6AAEF8C-B50E-4A15-9EAD-5AA5B4E9BA17.thumb.jpeg.546da19f8046a70b24dcd0358eb1bbd3.jpeg6F978CA0-F62E-4260-9401-D472FC9E9FBA.thumb.jpeg.74c2f807ac6c1bd9bfbb80ca7a9307e2.jpegAny way they look cool but there is a crappy friction coefficient with the aluminium body and the brass shaft so next is a ptfe or similar insert for the shaft to move more freely. Watch this space.

36256DF1-312B-4EB7-8968-01ED7635E196.jpeg

Edited by McCvinyl
New photo

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Nice work. looking forward to see what the next lot look and perform like. 

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For a fellow SNA member. A PT2308 based HP amp on Vera-brd. Mix of NP and LESR caps. 

6FF0DB7D-CEE0-460F-9AFA-19A269A33940.jpeg

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For a fellow SNA member. A PT2308 based HP amp on Vera-brd. Mix of NP and LESR caps. 
6FF0DB7D-CEE0-460F-9AFA-19A269A33940.thumb.jpeg.3c64e29b07e7c5031b919f9defc79770.jpeg

Going to a good home

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2 minutes ago, Benjet said:


Going to a good home emoji106.png

In the post today.

 

I got some more PT2308s. Not sure what to build next. I have a single ShuGuang 50 Year Treasure I could make another hybrid with. The rotten part is I have to make another PS also. 

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I have some IRF240s just wondering what I could do with those.

2SK170s, would they make a decent HP amp?

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I’d be looking for a schematic from someone who has done it. 

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Another LDR attenuator. This one uses arduino to create an attenuator that does not need matched LRD's and can be calibrated for perfect channel image and variable input impedance up to 50K ohms to match whatever amp your connecting it to. 

IMG_20190702_085433.thumb.jpg.d6c7fc6ec310fd0a479101bbdeab8eb6.jpgIMG_20190702_085416.thumb.jpg.662c3ebff7c14e6e8d30a191c2e8dff4.jpgIMG_20190702_085102.thumb.jpg.d8255489df3970b814312fe285172438.jpgIMG_20190702_085001.thumb.jpg.922ee098b3360f07b725ee5d38be7ed3.jpgIMG_20190702_084936.thumb.jpg.29908d94b8371042cabbe11c4dc311d3.jpgIMG_20190702_084914.thumb.jpg.19c7be4e0f453bb33b71ab6c795e472e.jpgIMG_20190702_084851.thumb.jpg.16bdd93095ae9267e490ae297bb39bdc.jpg

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These are not my pics, I 'borrowed' them from DIY audio to show the case. Just waiting on mine to turn up, PCBs completed just the mains voltage selector switch, Source selectoe extension and RCAs to come.

 

I must say I am quite impressed with the case just looking at the pictures.

 

1837898215_yarrafront.thumb.jpg.ccb51a3f7a828c3287f1d7dff8ec25d5.jpg

702645872_Yarrarear.thumb.jpg.03e9284bf56046e807572a7aab16c291.jpg

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Posted (edited)

There is no such thing as a free lunch and everything in audio is a compromise. In a number of preamps I have put the pot on the output. Though I use expensive pots they are all noisy. If on the input not only do you throw away some of the input signal and amplify what’s left but you also amplify the noisy pot. If on the output you attenuate the whole amplified signal but not the pot noise but if the input signal is too high it can overdrive and distort the signal. No free lunch.

 

Also when the pot is on the output (as I would prefer) your next stage will need an input cap because the output is not DC decoupled. This preamp “Elite” had the pot on the output and now Elite has an inbuilt headphone amp. The HP amp should have an input cap but if the pot is on the input then the preamp output cap is all that is required. In other words I can cut out one cap.

 

An hour or two of open heart surgery has moved the pot to the front of this expensive to build preamp and allowed me to connect the output of the tube stage directly to the HP amp driver stage just using the very expensive Jensen CuPIO caps which were already part of the this preamp. The pot is a premium stepper with high end Japanese resistors so any noise is going to be very low. 

 

When the HPs are plugged in the output RCAs (this is a preamp also) are disconnected to ensure the HP section and pure preamp drive do not effect each other. When there are no phones plugged in the output RCAs are live.

 

Should mention this preamp/HPamp with two inputs will go up for sale.

E99CC8CE-E426-4396-9E0C-DFAEF42610DF.jpeg

 

9D2447A3-44D5-4CC5-8C5B-1ED61DCC7FE9.jpeg

Edited by mwhouston

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Just finished up building my own focal centre speaker using flax drivers. The enclosure was an existing old mirage centre speaker I had laying around. I must say it does sound very good.

943FCA11-E671-44D2-A5B2-FB0DDD548727.jpeg

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Posted (edited)

Alpine subwoofer custom build. Running 1000 watts rms Velodyne amp. Really gives my monitor Audio sub a good run. For pure output I would say the Alpine wins. Not a bad little sealed enclosure.

 

 

A1FF03C2-7E00-4226-BBE9-78B566BBE495.jpeg

2EF4A544-FB16-4997-8F9A-A4E79F66C0D5.jpeg

AD5A959B-160D-46FB-9B45-5E40CABA2476.jpeg

1494CA81-A4DA-4D93-939D-2BE98886E3C9.jpeg

1D8B8996-4674-4EF4-B19B-F8708AAD8C49.jpeg

Edited by Paladin2k

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On 04/07/2019 at 3:23 PM, mwhouston said:

There is no such thing as a free lunch and everything in audio is a compromise. In a number of preamps I have put the pot on the output. Though I use expensive pots they are all noisy. If on the input not only do you throw away some of the input signal and amplify what’s left but you also amplify the noisy pot. If on the output you attenuate the whole amplified signal but not the pot noise but if the input signal is too high it can overdrive and distort the signal. No free lunch.

 

Also when the pot is on the output (as I would prefer) your next stage will need an input cap because the output is not DC decoupled. This preamp “Elite” had the pot on the output and now Elite has an inbuilt headphone amp. The HP amp should have an input cap but if the pot is on the input then the preamp output cap is all that is required. In other words I can cut out one cap.

 

An hour or two of open heart surgery has moved the pot to the front of this expensive to build preamp and allowed me to connect the output of the tube stage directly to the HP amp driver stage just using the very expensive Jensen CuPIO caps which were already part of the this preamp. The pot is a premium stepper with high end Japanese resistors so any noise is going to be very low. 

 

When the HPs are plugged in the output RCAs (this is a preamp also) are disconnected to ensure the HP section and pure preamp drive do not effect each other. When there are no phones plugged in the output RCAs are live.

 

Should mention this preamp/HPamp with two inputs will go up for sale.

E99CC8CE-E426-4396-9E0C-DFAEF42610DF.jpeg

 

9D2447A3-44D5-4CC5-8C5B-1ED61DCC7FE9.jpeg

Perhaps you could try using an LDR attenuator circuit instead of a pot or stepped attenuators.

No moving parts that would produce crackling and in some cases certain coupling capacitors may be not required either.

There are a lot of circuits out there already or you can design your own using the Silonex NSL-32SR2 or Silonex NSL-32SR3 available from element14.

I am in the process of doing an upgrade to my existing valve preamp but still using the Alps pot for control of the LDR's.

Worth looking into anyway.

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2 hours ago, MarcAL said:

Perhaps you could try using an LDR attenuator circuit instead of a pot or stepped attenuators.

No moving parts that would produce crackling and in some cases certain coupling capacitors may be not required either.

There are a lot of circuits out there already or you can design your own using the Silonex NSL-32SR2 or Silonex NSL-32SR3 available from element14.

I am in the process of doing an upgrade to my existing valve preamp but still using the Alps pot for control of the LDR's.

Worth looking into anyway.

Fortunately after the changes above all is good now. Good suggestion but. 

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Vacuum tube audio sp14 preamp with premium parts. 

 

Time to wire her up...

93DE4C31-6CDF-4B97-9B10-3907E9E1FD7D.jpeg

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